Various arrangements of the derrick cylinders are known for cranes with telescopic jibs. Auto cranes with telescopic jibs predominantly have a luffing cylinder arrangement located near the pivot of the jib. These cranes achieve maximum luffing angles and thus large lifting heights and lifting loads. With this arrangement of the luffing cylinder, the jibs are primarily stressed by compressive forces. In the horizontal operating position, the jib can be loaded only to a limited extent with this arrangement of the derrick cylinder.
With railroad cranes, the luffing cylinders are disposed in the front part of the crane superstructure, usually at a larger distance from the jib pivot. Thus, the maximum carrying capacity is reached when the jib is in its horizontal operating position. The attainable lifting height is limited by the excursion length of the working cylinders and by their arrangement.
DD Patent 145,850 discloses a solution with a telescopic jib in a swivel mounted guide piece. The guide piece is mounted in the front part of the crane superstructure and can be adjusted by means of a cable pulley.
The disadvantage of this solution is that the jib can be telescoped only in its horizontal operating position. In other operating positions, the jib is locked and the telescope cannot be used. Another disadvantage is that the large forces from the horizontal operating mode of the crane are unfavorably conducted through the luffing gear into the crane superstructure.
Another solution is disclosed in DD Patent No. 229,101. The lower section of a bendable jib is swivel mounted on the crane superstructure. The upper part of the jib is telescoped repeatedly and luffed about the bending point by the working cylinder.
The disadvantage of this solution is the great effort involved in setting up and in the special mounting of the derrick cylinders, which must detach from the upper section of the jib during the erection process. Furthermore, the expensive equipment for swinging the telescopic jib open and closed is another disadvantage, since the jib can be swung open only in the retracted state.
A less complicated jib system must be created which can be used in tightly constricted working spaces and with great lifting heights, which requires little erection effort, and which achieves high carrying capacity.